1. Field of the Invention
In one aspect, the present invention relates to the use of natural tissues as implantable materials for medical-surgical use. In a related aspect the present invention is directed generally to wraps for implants including intra orbital prosthetic ocular implants designed to be accommodated in the orbital cavity after enucleation and, particularly, an improved pre-formed wrap and method of making the wrap for an orbital implant that simplifies the implant procedure and produces a compatible and comfortable wrapped implant prosthesis. The invention contemplates the use of preformed, processed pouches for the wraps that are substantially spherical and which are constructed of natural bio-compatible animal tissue, preferably bovine pericardial tissue.
2. Related Art
Eyes severely damaged due to disease or trauma may have to be partially or totally removed and replaced by implant prostheses. In this manner, the damaged eye may be eviscerated, a procedure in which all of the inner contents are removed or, an enucleation may have to be performed in which the entire eyeball is removed after severing it from the eye muscles and the optic nerve. Typically, an artificial implant is fitted into the orbital socket to replace the volume in the orbit that was lost when the eye was removed. To this an artificial eye is fitted which is also attached to the eye muscles so that it will track with the normal eye. With evisceration, a sufficient amount of the patient""s own tissue may be available to contain or isolate the implant. In the case of enucleation, however, nothing remains inwardly of the patient""s own tissue to encase the implant prosthesis and a separate wrap must be provided.
The typical ocular orbital implants are made from natural or non-natural materials of various types including hydroxyapatite obtained from coral or manufactured by synthetic means, as illustrated in U.S. Pat. No. Re 34,307 to Perry. The implants also are also made from various synthetic polymer materials, such as a porous polyethylene. The generally spherical implants, in the case of an eviscerated eye, are normally inserted into the scleral sac of the patient""s own eye which remains attached and the sac is sewn closed about the implant. If, however, an enucleation or total removal of the eye has been performed, a replacement for the scleral sac must also be used in order for the implant to be isolated in order to prevent a foreign body reaction and protected from infection. Many materials have been used for such replacement scleral sacs including material earlier removed from the patient or received from an eye bank. While these and other materials including flat sections of animal tissue have been used with some success, it is difficult and time-consuming to form such materials into the proper spherical shapes during surgical implantation procedures.
There remains a need for an orbital implant wrap or sac device which is pre-formed to the proper spherical shape with respect to receiving an ocular implant for replacement of a removed eyeball.
Accordingly, it is a primary object of the present invention to provide a pre-formed orbital implant wrap or sac for an ocular implant prosthesis that is pre-formed to fit an ocular prosthesis and the eye socket.
Another object of the present invention is to provide a pre-formed crosslinked wrap for an ocular prosthesis that is processed from bovine pericardial tissue.
Other objects and advantages will occur to those skilled in the art upon becoming familiar with the specification, drawings and appended claims herein.
On a separate subject, Applicant""s own prior patents and applications related generally to the use of animal tissues (e.g., U.S. Pat. No. 4,456,589), including for such purposes as staple buttresses (U.S. Pat. Nos. 5,503,638; 5,549,628; 5,575,803; and vascular grafts (U.S. Pat. No. 4,915,113), and stent covers (International Application Serial No. PCT/US98/25674) the disclosures of each of which are incorporated herein by reference.,
In accordance with the present invention, it has been discovered that certain natural animal tissues, properly preserved and processed, present superior properties for pre-formed implants, including wraps. In the case of ocular orbital implants, in particular, it has been found that if the implant wraps are pre-formed in a spherical shape and the tissue processed or crosslinked, in the pre-formed shape a superior wrap is produced which facilitates the implant procedure. In particular, bovine pericardial tissue has been used quite successfully. The processed orbital implant wraps of the invention are sterile and ready to receive implants and can be readily situated and attached in place. They can be produced in all convenient sizes required.
The invention further contemplates a process for forming and crosslinking pre-shaped orbital implant wraps or spherical sacs which results in implantable sacs shaped to precisely receive spherical implants in a variety of sizes and to be received and secured to or as a replacement for the scleral sac of a patient.
It will be appreciated that the process for manufacturing orbital implant wraps in the pre-formed state in accordance with the process of the present invention results in an easier and less time consuming artificial eye implant procedure.
In the process of the present invention the orbital implant wraps are formed from pre-soaked or dehydrated animal tissue using generally spherical shaping forms of desired sizes. The generally spherical forms are wrapped with the material which is secured in place in a manner which preserves an implant inlet opening. The tissue is thereafter crosslinked in place, removed from the form and the opening shaped in the pre-formed, generally spherical sac. The wraps are then rinsed, sterilized and packaged for shipment in a water solution or, alternatively, processed to a dry state as by vacuum drying and terminally sterilized in the package, e.g., by gamma irradiation or electron beam (E-beam) sterilization.
In one process, the tissue is dehydrated by placing in 95 percent and then 70 percent ethanol prior to wrapping on the spherical form. The wrapped spheres are further soaked in 70 percent ethanol prior to crosslinking. In an alternate process, the tissue is presoaked in low concentration of glutaraldehyde solution before wrapping and without exposure to ethanol or other dehydrating chemicals.
The preferred material for the wraps of the invention is bovine pericardial tissue and this may be either frozen or freshly harvested. The shaping sphere is of a material that is compatible with the bovine pericardial sac tissue and resistant to the other materials used in the process. Thermoplastic acetal resins, particularly those sold under the trademark Delrin, have been successfully employed.